Induction-motor.



R. Ej-HLLLMUND. INDUCTION MOTOR. "APPLICATION FILED AUG.2, 1909.

T .ll-m V0E 1S VS Huw/.JZ NB H. .dus .n UwnoH D 8 m D1 J f Y L L INVENTOH /u vif f5/222mm@ WITNESSES:

R. E. HELLMUND. INDUCTION MOTOR.` APPLGATION FILED AUG. 2. 1m.

3 SHEETS-SHEET 2.'

atented Nov. 10, 1914.

R. B. HELLMUND. INDUQTIONv MOTOR. APPLICATION FILED AU G.2, 1909.

a sHBgTs-SHEBT s.

4INVENTOR Patented Nov. 10,1914..

' a resident, of Pittsburgh, in the count onirEn STATES' PATENT oFFioE.

.iR-UDOLF E. BELLI/LUNE, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, OF PITTSBURGH, PENNSYL- I; VANIA, A CORPORATION OF PENNSYLVANIA.

INDUCTION-MOTOR.

To all whom it may concern.' y Be it known that I, RUDOLF E. HELL- MUND, a subject of the German Empire, and

o Allegheny and State of Pennsylvania, ave invented a new and useful Improvement in Induction-Motors, of which the following is a specification.

My invention relates'to dynamo electric` machines, and particularly to non-sychronous alternating-current motors. y

The object of my invention is to'provide an improved secondary winding of the squirrel-cage type for multi-speed induction motors, whereby the slip andthe torque of the motor for each speed may be independently predetermined to accommodate special conditions of operation. y

The primary windings of induction motors are frequently adapted for producing two or .three different numbers of poles inV order to provide 'for different operating speeds. Under these conditions, if the usual form of squirrel-cage secondary windings is employed, the slip, or the difference between the actual speed and the synchronous speed, is considerable for thev higher speeds and is less for the lower speeds. In some cases, however, it is desirable to reduce the slip for the higher speeds and to materially increase the slip for the lower speeds.

In' order to accomplish the aforesaid ob- -jective results, I provide, in addition to the end-connecting rings of the rotor, one or more auxiliary rings, which` only inter-connect certain groups of barsiinstead of being connected to all of the bars, the circuit connections being such that the auxiliary rings are only active when the machine is operating at the higher speed or speeds.

Figure 1 of-the accompanying drawings is a diagrammatic view of an induction motor embodying my invention. Fig. 2 is a partial, sectional elevation of a rotor corresponding to that shown diagrammatieally in Fig. 1. Fig. 3 is a diagrammatic view of a rotor windin -whichv may be used in connection with` a four-speed motor. Fig. 4 is a yview corresponding to Fig. 2 of a rotor having al modified form of Winding embodying m invention. Fig. 5 is a sectional elevation 'o 'a portion of an induction motorfdis'clos- Specification of Letters Patent.

Patented N 0V. 10, 1914.

Application filed August 2, 1909. Serial No. 510,840.

pole double throw switch- 4 being providedl for changing the stator connections in order to produce two .different numbers of magnetic poles and two different operating speeds for the motor. The rotor 5 comprises a core member 6, having a plurality of peripheral slots 7 and a winding composed of bars 8 of conducting material located in the slots 7, and end connecting rings 9, 10, 11 and 12. The stator winding is similar to that described in Patent No. 811,644, granted February 6, 1906, to the Westinghouse Electric & Manufacturing Company, upon an application filed ley-Benjamin G. Lamme, and it may be replaced by any suitable stator winding which is adapted to produce more than one number of magnetic poles, means being provided for producing any one of the desired polar combinations.- In the stator winding shown, A A and BB are the terminals of two portions of the main prima-ry winding which are respectively connected to the contact terminals c d, e and o ofthe double-throw switch 4, :End C C are the terminals of the auxiliary primary Winding which are respectively connected to the contact terminals c and f of the said switch. An external resistance element R is included in the connection between the terminal C andthe contact terminal f, but this resistance may be omitted' if the auxiliary wind? soV the position of the switch 4 is reversed, the

primary windings are connected in p rallel, the current in the winding B B bei g reversed in direction and the number of poles being thereby changed from twelve to six.-

The auxiliary winding and its resistance R are also excluded from the circuit. The circuit connections of the rotor, and partie` ularlythose of the end connecting rings 11 and 12, are clearly set forth inthe diagram ot F ig. 1 in which the bars 8 are represented by la series of parallel lines and the rings are represented by lines that cross the bars, with which they come in contact, at right angles. The bars'S may be divided into a series ot' groups a and Z), each of the groups being composed of 'those bars which are included within the pole pitch ot the 12- pole stator winding and each pair of adjacent groups a and b being composed of those bars which are included within the pole pitch of the spole stator winding. It will be observed. that ring 11 interconnects groups a of the bars 8, that alternate with groups b, which are interconnected by the ring 12. The directions of current which the poten` tials induced in the rotor tend to produce in the bars 8, when the motor is operating as a 12-pole machine, are indicated by the arrows 13, and those produced when the motor is operating as a 6-pole machine are indicated by arrows 131. `When the motor is operating as a l2-pole machine, there is no possibility of an interchange of large currents through the rings 11 and 12, since the direction of current in all the bars connected by each ring is approximately trie same, as indicated by the arrows 13. it, however, the motor is operating as a G-pole machine, currents of opptsitc direction tend to flow through adjacent groups a of the bars 8 which are connected by the same ring, as indicated by the arrows 1311, and hence there is a transfer of current between thegroups, not only through lthe end rings 9 and 10, but also through the auxiliary rings 11 and 12. By suitably proportioning the resistances of the rings t), 10, 11 and 12 the slip oi the motor at the highest speed, that is, when operating with six poles, .may be made relatively slight since the rings 11 and 12 are connected in parallel relation to the rings El and 10, and the slip of the motor may be made relatively large when the machine is operating with twelve poles since the rings 11 and 12 are then inactive.

lt is evident that the arrangement described above may be advantageously utilized for starting induction motors when a rela` tively large starting torque is essential.

Auxiliary rings corresponding` to rings 11 and 12 may.y oi' course, be provided adjacent to the ring 9 it' the electrical or mechanical 'design of the machine renders a symmetrical arrangement desirable.

In the diagram of Fig. 3, auxiliary rings 14` 15, 16 and 17 are employed in lieu of the rings 11 and 12 ot Fig. 1, the bars 8 in this diagram being divided into two sets of groups c and o, and c and d so that the slip of the motor may be predetermined and adrilassa When a relatively large torque at a slow 1 speed is desired for starting purposes, or in some other cases, 1t may be found advantageous to provide an independent starting winding in order that its resistance may.

be materially increased without danger of destroying the end connecting rings. An arrangement of this kind is illustrated in Fig. 4. The bars 18 and the end connecting rings 19 and 2O constitute the starting windingr and the bars 21 and the rings 22, 23, 24

' ano 25 constitute the high-speed operating winding. vWhen operating at the lower speed, only the higlrresistance winding will be active (the circuit connections of the rings 22, 23, 24 and 25 corresponding to those of the rings 11 and 12) and, when the machine is operating/at its higher speed, both windings will be active.

Referring to Figs. 5 and 6 of the draw- 'ngs, inv which corresponding parts are designated by the same reference characters as those employed in the other figures, the core member 6 of the rotor is mounted on a spider 26 and is held in place by end plates or rings 46 and 47. The stator comprises a stationary frame 27, a core member 28, a primary winding 29. and end bells 30 and 31. Bars 8 are located in the usual core slots of the rotor and are interconnected by means of zigzag straps 33 and 34 ot conducting material, which are secured to the bars at their ends and constitute relarings 11 and 12, lcorresponding to those shown in Fig. 2 of the drawings, are also secured to the bars 8, but are located relatively close tothe core member 6. A pair of bafiie plates 35 and 36 are mounted on a shaft 48 and extend outwardly between the rings 11 and the rings 33 and 34. Stationary baille plates 37 and 38 are secured to the end bells 30 and 31, respectively, and `project iio inwardly` so that their edges are substantially opposite the edges of the baille plates 35 and 36. By this means, Ventilating passages' are provided from a point near the shaft 48, through a .plurality of holes 39 and 40, which are provided in the plates 35 and 36, and out through holes 41 and 42 which are provided in the end bells. At they same time, the high-resistance rings 33 and are ventilated by drafts of air which are directed from openings 49 through the outer chambers 43 and 44 to openings 50 of the end bells. The principal advantage of-fthis `arrangen-lent is due| to the fact that the heat generated in the high-resistance rings. 33

105 tively high-resistance end rings. Auxiliary sets of Correction in Letters Patent No.j1,l 16,424.

.drawings and that changes may be made in the circuit connections shown without dey. p parting from the spirit of my invention. I

desire that only such limitationsshall be imposed as are indicated in the appended claims. .o

I claim as my invention:

ll'. In an induction motor, the combination I with a primary Winding adapted to produce ap urality of polar-combinations, of a secondary winding comprislng a pluralit of bara/end connecting rings therefor, an auxiliary rings for connecting the bars in groups.

2. A secondary winding for non-synchronous motors comprising a plurality of rods or bars, end rings for connecting said bars, and auxiliary rings which permanently connect saidbars in two sets o equal and 'alter-4 natel disposed groups.

3. n an induction motor, -the combina-` tion with a `primary winding adapted to produce a lurality of polar combinations, of a secon ary winding comprising a plu- .rality of rods or bars, end rings for connecting said bars, and auxiliary rings which permanently connect said' bars 1n two sets of equal groups.

4. The induction motor, the combination with a rimary winding adapted to produce a plur ity of polar combinations, of a secondary winding comprising a plurality of rods or bars, end connecting ringsvfor said bars of reljatively high resistance, and auxan improvement in' (Induction-Motors,

r 1914, upon the application of Rudolf E. Hellmu-nd, of Pittsburgh,Pennsylvania,

cation lrequiring correction as follows: Page 3', line 74, for the word and iliary end connecting rin which act as a shunt for said first name rings only when a certain polar combination obtains.

y V5. 'In an induction motor, in combination with a primary winding adapted to produce a plurality 'of polar. combinations, a

. secondary winding comprising a plurality of bars divided into groups, means for connecting said bars to conduct currents in the same direction in adjacent groups when a certain polar combination obtains and to conduct currents kkin opposite direci tions in said adjacent groups w en a second polar combination obtains.

6. In an induction motor, in combination with a rimary winding adapted to produce a plura ity .of polar combinations, of a secondary winding comprising a plurality .of rods 4or'bars divided into two sets of groups, and means for connecting the groups of each of said sets to correspond-to the poles in one polar v"combination, and means for connecting said bars to adapt adjacent airs of said groups to correspond to the po es when( a second polar combination obtains.

7. In an induction motor, 1n combination with a primary .winding adapted to produce a plurality of polar combinations for ef fecting motor speed adjustments, of a sec-A ondary winding comprising a lurality of bars, and connecting rings t 1ere or and aux'- iliary rings for connecting the bars in Isuch groups as to constitute a plurality of shuntcircuitsto the end rings only when predetermined polar combination obtain.

In testimonv whereof, I havev hereunto' name this 28th day of July, 80

subscribed my 1909.

. R. E. HELLMUND.

Witnesses:

CHARLES W. MCGHEE, R. J. DaAnnonN.

4It'i's hereby certified that in Letters'tatent No.A 1,116,424, granted November 10,

for

an error appears in the printed 'specifiread and; and that the said Letters Batent should be read with this v,correction therein that the saine may conform to the record of the case in the Patent Office.

` Signed and sealed this 15th day of December, A. D.,1914.

J. T. NEWTON,

Acting Commissioner of Patents. 

